Physiological, Ecological, and Biochemical Implications in Tomato Plants of Two Plant Biostimulants: Arbuscular Mycorrhizal Fungi and Seaweed Extract

Root symbiotic fungi improve nitrogen transfer and morpho-physiological performance in Chenopodium quinoa

Root-associated fungal endophytes may facilitate nitrogen (N) absorption in plants, leading to benefits in photosynthesis and growth. Here, we investigated whether endophytic insect pathogenic fungi (EIPF) are capable of transferring soil N to the crop species Chenopodium quinoa. We evaluated nutrient uptake, carbon allocation, and morpho-physiological performance in C. quinoa in symbiosis with two different EIPF (Beauveria and Metarhizium) under contrasting soil N supply. A controlled experiment was conducted using two plant groups: (1) plants subjected to low N level (5 mM urea) and (2) plants subjected to high N level (15 mM urea). Plants from each group were then inoculated with different EIPF strains, either Beauveria (EIPF1+), Metarhizium (EIPF2+) or without fungus (EIPF-). Differences in N and C content, amino acids, proteins, soluble sugars, starch, glutamine synthetase, glutamate dehydrogenase, and physiological (photosynthesis, stomatal conductance, transpiration), and morphological performance between plant groups under each treatment were examined. We found that both Beauveria and Metarhizium translocated N from the soil to the roots of C. quinoa, with positive effects on photosynthesis and plant growth. These effects, however, were differentially affected by fungal strain as well as by N level. Additionally, an improvement in root C and sugar content was observed in presence of EIPF, suggesting translocation of carbohydrates from leaves to roots. Whereas both strains were equally effective in N transfer to roots, Beauveria seemed to exert less demand in C. quinoa for photosynthesis-derived carbohydrates compared to Metarhizium. Our study revealed positive effects of EIPF on N transfer and morpho-physiological performance in crops, highlighting the potential of these fungi as an alternative to chemical fertilizers in agriculture systems.

Differential impacts of interactions between Serendipita indica, Chlorella vulgaris, Ulva lactuca and Padina pavonica on Basil (Ocimum basilicumL.)

Plant biostimulants (PBs) are used globally to increase crop yield and productivity. PBs such as (Serendipita indica) or algal extracts stimulate and accelerate plant physiological processes. The physiological, ecological, and biochemical effects of (Serendipita indica) or algal extracts individually and in combination on basil plant (Ocimum basilicum L.) were investigated. Macroalgae samples were collected from Abu Qir, Alexandria, Egypt. The growth parameters, chlorophyll index, and biochemical composition of basil were analyzed at 90th day. The (Chlorella vulgaris) + (Serendipita indica) (MI + F) treatment increased chlorophyll index by 61.7% (SPAD) compared to control. (Chlorella vulgaris) had the highest growth hormones, including GA3 at 158.2 ppb, GA4 at 149.1 ppb, GA7 at 142.6 ppb, IAA at 136.6 ppb, and TC at 130.9 ppb, while (Ulva lactuca) had the lowest. The MI + F treatment yielded the highest essential oil and antioxidant values. Treatment with (Chlorella vulgaris) increased S. indica colonization by 66%. In contrast, Ulva lactuca and (Padina Pavonica) inhibited S. indica colonization by 80% and 40%, respectively. (Ulva lactuca) and (Padina Pavonica) inhibited S. indica colonization by 80% and 40%, respectively. Combined treatments had a greater influence on basil performance than the individual treatments. The evidence of synergistic/additive benefits to plants performance due to the interactive effects of (Chlorella vulgaris) and (Serendipita indica) had been studied. Complementary modes of action between (Chlorella vulgaris) and (Serendipita indica), through their components newly emerging properties on basil, may explain observed synergistic effects. This study explores the potential of microbial-algal interactions, particularly (Chlorella vulgaris) and (Serendipita indica), as innovative plant biostimulants. These interactions demonstrate positive effects on basil growth, offering promise for more effective microbial-based formulations to enhance crop productivity and sustainability in agriculture. These novelties will help create a second generation of PBs with integrated and complementary actions.

Improvement of rooting and growth in kiwifruit (Actinidia deliciosa) cuttings with organic biostimulants

Seaweed extracts have shown profoundly positive effects on crop growth, quality and reproduction in diverse agricultural and horticultural crops. Seaweed extracts can be used to promote the rooting and growth of cuttings in perennial fruit species like kiwifruit (Actinidia deliciosa). In this study, the cuttings were treated with 1, 5, 10 and 50% solutions of G Sap (Gracilaria edulis), K Sap (Kappaphycus alvarezii), AN (Ascophyllum nodosum), EM (Ecklonia maxima), HA (Humic acid) and control (water) for 6 h as base dipping. Subsequently, the treatments of G Sap, K Sap, AN, EM, HA and control were repeated every 15 days for a period of six months as application of 50 ml solutions in the potted cuttings. All the treatments exhibited significant effects on the rooting percent in all the kiwifruit cultivars, namely 'Monty', 'Abott', 'Hayward', 'Allison' and 'Bruno' (P ≤ 0.01) as compared to the control. Shoot and root growth parameters including leaf number per cutting, number of roots per cutting, number of branches, plant height, shoot diameter, root length, root diameter and root weight were all positively increased with the application of seaweed extracts (P ≤ 0.05). Cuttings treated with seaweed extract exhibited significantly higher levels of pigments (chlorophyll a, chlorophyll b and total carotenoids), metabolites (total carbohydrates and soluble phenols) and less electrolyte leakage as compared to the control cuttings. Significant positive and negative correlations were observed between biochemical parameters combined with plant nutrient concentration. Principal component analysis (PCA) revealed that PC1 and PC2 (first two principal components) accounted for 75% of the entire variation. While, PC1 accounted for 63% of the total variation, PC2 accounted for 11% of the total variation. The leaves and the roots of kiwifruit cultivar 'Hayward' treated with G Sap at 10%, K Sap at 10%, AN at 10%, EM at 10%, HA at 10% exhibited higher expression of all four root promoting candidate genes (GH3-3, LBD16, LBD29 and LRP1) compared to the control. Therefore, it can be concluded that, seaweed extract and humic acid can be used as a suitable alternative to synthetic hormones for promoting the rooting and growth of kiwifruit cuttings.

Application of seaweed extracts to mitigate biotic and abiotic stresses in plants

Agriculture sector is facing a lot of constraints such as climate change, increasing population and the use of chemicals, and fertilizers which have significant influence on sustainability. The excessive usage of chemical fertilizers and pesticides has created a significant risk to humans, animals, plants, and the environment. To reduce the dependency on chemical fertilizers and pesticides a biological-based alternative is required. Seaweeds are essential marine resources that contain bioactive compounds and they have several uses in agriculture. The use of seaweed extracts in agriculture can mitigate stress, enhance nutrient efficiency, and boost plant growth. The use of seaweed extracts and their components activate several signaling pathways and defense-related genes/enzymes. In this review, an attempt has been made to explain how seaweed extracts and their bioactive components induce tolerance and promote growth under stress conditions.

The Functional Profile and Antioxidant Capacity of Tomato Fruits Are Modulated by the Interaction between Microbial Biostimulants, Soil Properties, and Soil Nitrogen Status

The application of microbial biostimulants to plants has revealed positive effects related to nutrients uptake, stress tolerance, root development and phenological growth. However, little information is available exploiting the potential synergistic biostimulant action of microbes on the functional quality of the yields. The current research elucidated the effect of single or coupled action of biostimulants, associated with either optimal or reduced nitrogen application, on the functional quality of tomato fruits. Chemical assays and untargeted metabolomics were applied to investigate Rhizoglomus irregulare and Funneliformis mosseae administration (both being arbuscular mycorrhiza, AMF), under optimal or low N input conditions, alone or coupled to Trichoderma atroviride application. The coupling of AMF and Trichoderma fungal inoculations resulted in a synergistic biostimulant effect on tomato fruits under sub-optimal fertility, revealing improved concentrations of carotenoid compounds-B-carotene (0.647 ± 0.243 mg/100 g), Z-carotene (0.021 ± 0.021 mg/100 g), 13-z-lycopene (0.145 ± 0.052 mg/100 g) and all-trans-lycopene (12.586 ± 1.511 mg/100 g), and increased values for total phenolic content (12.9 ± 2.9 mgGAE/g), total antioxidant activity (phosphomolybdenum, 0.9 ± 0.2 mmolTE/g), radical scavenging activity (DPPH, 3.4 ± 3.7 mgTE/g), reducing power (FRAP, 23.6 ± 6.3 mgTE/g and CUPRAC, 37.4 ± 7.6 mg TE/g), and enzyme inhibitory activity (AChE, 2.4 ± 0.1 mg GALAE/g), when compared to control. However, evidence of carotenoid and bioactive compounds were exclusively observed under the sub-optimal fertility and no significant differences could be observed between the biostimulant treatment and control under optimal fertility.

Mycorrhizal Effects on Growth and Expressions of Stress-Responsive Genes (aquaporins and SOSs) of Tomato under Salt Stress

Environmentally friendly arbuscular mycorrhizal fungi (AMF) in the soil can alleviate host damage from abiotic stresses, but the underlying mechanisms are unclear. The objective of this study was to analyze the effects of an arbuscular mycorrhizal fungus, Paraglomus occultum, on plant growth, nitrogen balance index, and expressions of salt overly sensitive genes (SOSs), plasma membrane intrinsic protein genes (PIPs), and tonoplast intrinsic protein genes (TIPs) in leaves of tomato (Solanum lycopersicum L. var. Huapiqiu) seedlings grown in 0 and 150 mM NaCl stress. NaCl stress severely inhibited plant growth, but P. occultum inoculation significantly improved plant growth. NaCl stress also suppressed the chlorophyll index, accompanied by an increase in the flavonoid index, whereas inoculation with AMF significantly promoted the chlorophyll index as well as reduced the flavonoid index under NaCl conditions, thus leading to an increase in the nitrogen balance index in inoculated plants. NaCl stress regulated the expression of SlPIP1 and SlPIP2 genes in leaves, and five SlPIPs genes were up-regulated after P. occultum colonization under NaCl stress, along with the down-regulation of only SlPIP1;2. Both NaCl stress and P. occultum inoculation induced diverse expression patterns in SlTIPs, coupled with a greater number of up-regulated TIPs in inoculated versus uninoculated plants under NaCl stress. NaCl stress up-regulated SlSOS2 expressions of mycorrhizal and non-mycorrhizal plants, while P. occultum significantly up-regulated SlSOS1 expressions by 1.13- and 0.45-fold under non-NaCl and NaCl conditions, respectively. It was concluded that P. occultum inoculation enhanced the salt tolerance of the tomato, associated with the nutrient status and stress-responsive gene (aquaporins and SOS1) expressions.

The Effects of the Microbial Biostimulants Approved by EU Regulation 2019/1009 on Yield and Quality of Vegetable Crops

The use of microbial biostimulants such as plant growth-promoting rhizobacteria (PGPB) and arbuscular mycorrhizal fungi (AMF) has gained popularity in recent years as a sustainable approach to boost yield as well as the quality of produce. The beneficial effects of microbial biostimulants have been reported numerous times. However, information is missing concerning quantitative assessment of the overall impact of microbial biostimulants on the yield and quality of vegetable crops. Here we provide for the first time a comprehensive, semi-systematic review of the effects of microbial biostimulants allowed by Regulation (EU) 2019/1009, including microorganisms belonging to the AMF (phylum Glomeromycota), or to Azospirillum, Azotobacter and Rhizobium genera, on vegetable crops' quality and yield, with rigorous inclusion and exclusion criteria based on the PRISMA method. We identified, selected and critically evaluated all the relevant research studies from 2010 onward in order to provide a critical appraisal of the most recent findings related to these EU-allowed microbial biostimulants and their effects on vegetable crops' quality and yield. Moreover, we highlighted which vegetable crops received more beneficial effects from specific microbial biostimulants and the protocols employed for plant inoculation. Our study is intended to draw more attention from the scientific community to this important instrument to produce nutrient-dense vegetables in a sustainable manner. Finally, our semi-systematic review provides important microbial biostimulant application guidelines and gives extension specialists and vegetable growers insights into achieving an additional benefit from microbial biostimulant application.

A Seaweed Extract-Based Biostimulant Mitigates Drought Stress in Sugarcane

Drought is one of the most important abiotic stresses responsible for reduced crop yields. Drought stress induces morphological and physiological changes in plants and severely impacts plant metabolism due to cellular oxidative stress, even in C4 crops, such as sugarcane. Seaweed extract-based biostimulants can mitigate negative plant responses caused by drought stress. However, the effects of foliar application of such biostimulants on sugarcane exposed to drought stress, particularly on plant metabolism, stalk and sugar yields, juice purity, and sugarcane technological quality, have received little attention. Accordingly, this study aimed to evaluate the effects of foliar application of a seaweed extract-based biostimulant on late-harvest sugarcane during the driest period of the year. Three experiments were implemented in commercial sugarcane fields in Brazil in the 2018 (site 1), 2019 (site 2), and 2020 (site 3) harvest seasons. The treatments consisted of the application and no application of seaweed extract (SWE) as a foliar biostimulant in June (sites 2 and 3) or July (site 1). The treatments were applied to the fourth ratoon of sugarcane variety RB855536 at site 1 and the fifth and third ratoons of sugarcane variety SP803290 at sites 2 and 3, respectively. SWE was applied at a dose of 500 ml a.i. ha-1 in a water volume of 100 L ha-1. SWE mitigated the negative effects of drought stress and increased stalk yield per hectare by up to 3.08 Mg ha-1. In addition, SWE increased stalk sucrose accumulation, resulting in an increase in sugar yield of 3.4 kg Mg-1 per hectare and higher industrial quality of the raw material. In SWE-treated plants, Trolox-equivalent antioxidant capacity and antioxidant enzyme activity increased, while malondialdehyde (MDA) levels decreased. Leaf analysis showed that SWE application efficiently improved metabolic activity, as evidenced by a decrease in carbohydrate reserve levels in leaves and an increase in total sugars. By positively stabilizing the plant's cellular redox balance, SWE increased biomass production, resulting in an increase in energy generation. Thus, foliar SWE application can alleviate drought stress while enhancing sugarcane development, stalk yield, sugar production, and plant physiological and enzymatic processes.

Harnessing Synergistic Biostimulatory Processes: A Plausible Approach for Enhanced Crop Growth and Resilience in Organic Farming

Simple Summary

Demand for organically grown crops has risen globally due to its healthier and safer food products. From a sustainability perspective, organic farming offers an eco-friendly cultivation system that minimizes agrochemicals and producing food with little or no environmental footprint. However, organic agriculture’s biggest drawback is the generally lower and variable yield in contrast to conventional farming. Compatible with organic farming, the selective use of biostimulants can close the apparent yield gap between organic and conventional cultivation systems. A biostimulant is defined as natural microorganisms (bacteria, fungi) or biologically active substances that are able to improve plant growth and yield through several processes. Biostimulants are derived from a range of natural resources including organic materials (composts, seaweeds), manures (earthworms, fish, insects) and extracts derived from microbes, plant, insect or animal origin. The current trend is indicative that a mixture of biostimulants is generally delivering better growth, yield and quality rather than applying biostimulant individually. When used correctly, biostimulants are known to help plants cope with stressful situations like drought, salinity, extreme temperatures and even certain diseases. More research is needed to understand the different biostimulants, key components, and also to adjust the formulations to improve their reliability in the field.

Abstract

Demand for organically grown food crops is rising substantially annually owing to their contributions to human health. However, organic farm production is still generally lower compared to conventional farming. Nutrient availability, content consistency, uptake, assimilation, and crop responses to various stresses were reported as critical yield-limiting factors in many organic farming systems. In recent years, plant biostimulants (BSs) have gained much interest from researchers and growers, and with the objective of integrating these products to enhance nutrient use efficiency (NUE), crop performance, and delivering better stress resilience in organic-related farming. This review gave an overview of direct and indirect mechanisms of microbial and non-microbial BSs in enhancing plant nutrient uptake, physiological status, productivity, resilience to various stressors, and soil-microbe-plant interactions. BSs offer a promising, innovative and sustainable strategy to supplement and replace agrochemicals in the near future. With greater mechanistic clarity, designing purposeful combinations of microbial and non-microbial BSs that would interact synergistically and deliver desired outcomes in terms of acceptable yield and high-quality products sustainably will be pivotal. Understanding these mechanisms will improve the next generation of novel and well-characterized BSs, combining microbial and non-microbial BSs strategically with specific desired synergistic bio-stimulatory action, to deliver enhanced plant growth, yield, quality, and resilience consistently in organic-related cultivation.

Cacao (Theobroma cacao L.) Response to Water Stress: Physiological Characterization and Antioxidant Gene Expression Profiling in Commercial Clones

The increase in events associated with drought constraints plant growth and crop performance. Cacao (Theobroma cacao L.) is sensitive to water deficit stress (DS), which limits productivity. The aim of this research was to characterise the response of seven (CCN51, FEAR5, ICS1, ICS60, ICS95, EET8, and TSH565) commercially important cacao clones to severe and temporal water deficit stress. Ten-month-old cacao trees were submitted to two treatments: well-watered and water-stressed until the leaf water potential (Ψ leaf) reached values between -3.0 and -3.5 MPa. The effects of hydric stress on water relations, gas exchange, photochemical activity, membrane integrity and oxidative stress-related gene expression were evaluated. All clones showed decreases in Ψ leaf, but TSH565 had a higher capacity to maintain water homeostasis in leaves. An initial response phase consisted of stomatal closure, a general mechanism to limit water loss: as a consequence, the photosynthetic rate dropped by approximately 98% on average. In some clones, the photosynthetic rate reached negative values at the maximum stress level, evidencing photorespiration and was confirmed by increased intracellular CO2. A second and photosynthetically limited phase was characterized by a drop in PSII quantum efficiency, which affected all clones. On average, all clones were able to recover after 4 days of rewatering. Water deficit triggered oxidative stress at the early phase, as evidenced by the upregulation of oxidative stress markers and genes encoding ROS scavenging enzymes. The effects of water deficit stress on energy metabolism were deduced given the upregulation of fermentative enzyme-coding genes. Altogether, our results suggest that the EET8 clone was the highest performing under water deficit while the ICS-60 clone was more susceptible to water stress. Importantly, the activation of the antioxidant system and PSII repair mechanism seem to play key roles in the observed differences in tolerance to water deficit stress among clones.

Microbial Biostimulants as Response to Modern Agriculture Needs: Composition, Role and Application of These Innovative Products

An increasing need for a more sustainable agriculturally-productive system is required in order to preserve soil fertility and reduce soil biodiversity loss. Microbial biostimulants are innovative technologies able to ensure agricultural yield with high nutritional values, overcoming the negative effects derived from environmental changes. The aim of this review was to provide an overview on the research related to plant growth promoting microorganisms (PGPMs) used alone, in consortium, or in combination with organic matrices such as plant biostimulants (PBs). Moreover, the effectiveness and the role of microbial biostimulants as a biological tool to improve fruit quality and limit soil degradation is discussed. Finally, the increased use of these products requires the achievement of an accurate selection of beneficial microorganisms and consortia, and the ability to prepare for future agriculture challenges. Hence, the implementation of the microorganism positive list provided by EU (2019/1009), is desirable.

Alkaline extract of the seaweed Ascophyllum nodosum stimulates arbuscular mycorrhizal fungi and their endomycorrhization of plant roots

Ascophyllum nodosum extracts (ANE) are well-established plant biostimulants that improve stress tolerance and crop vigour, while also having been shown to stimulate soil microbes. The intersection of these two stimulatory activities, and how they combine to enhance plant health, however, remains poorly understood. In the present study, we aimed to evaluate: (1) the direct effect of ANE on the arbuscular mycorrhizal fungus Rhizophagus irregularis, and (2) whether ANE influences endomycorrhization in plants. ANE enhanced development of R. irregularis in vitro, showing greater spore germination, germ tube length, and hyphal branching. Greenhouse-grown Medicago truncatula drench-treated with ANE formed mycorrhizal associations faster (3.1-fold higher mycorrhization at week 4) and grew larger (29% greater leaf area by week 8) than control plants. Foliar applications of ANE also increased root colonization and arbuscular maturity, but did not appear to enhance plant growth. Nonetheless, following either foliar or drench application, M. truncatula genes associated with establishment of mycorrhizae were expressed at significantly higher levels compared to controls. These results suggest that ANE enhances mycorrhization through both direct stimulation of arbuscular mycorrhizal fungus growth and through stimulation of the plant's accommodation of the symbiont, together promoting the establishment of this agriculturally vital plant-microbe symbiosis.

Arbuscular Mycorrhiza-Mediated Regulation of Polyamines and Aquaporins During Abiotic Stress: Deep Insights on the Recondite Players

Environmental stresses of (a)biotic origin induce the production of multitudinous compounds (metabolites and proteins) as protective defense mechanisms in plants. On account of the regulation of some of these compounds, arbuscular mycorrhizal fungi (AMF) reinforce the inherent tolerance of plants toward the stress of different origins and kind. This article reviews two specific fundamental mechanisms that are categorically associated with mycorrhiza in alleviating major abiotic stresses, salt, drought, and heavy metal (HM) toxicity. It puts emphasis on aquaporins (AQPs), the conduits of water and stress signals; and polyamines (PAs), the primordial stress molecules, which are regulated by AMF to assure water, nutrient, ion, and redox homeostasis. Under stressful conditions, AMF-mediated host AQP responses register distinct patterns: an upregulation to encourage water and nutrient uptake; a downregulation to restrict water loss and HM uptake; or no alterations. The patterns thereof are apparently an integrative outcome of the duration, intensity, and type of stress, AMF species, the interaction of fungal AQPs with that of plants, and the host type. However, the cellular and molecular bases of mycorrhizal influence on host AQPs are largely unexplored. The roles of PAs in augmenting the antioxidant defense system and improving the tolerance against oxidative stress are well-evident. However, the precise mechanism by which mycorrhiza accords stress tolerance by influencing the PA metabolism per se is abstruse and broadly variable under different stresses and plant species. This review comprehensively analyzes the current state-of-art of the involvement of AMF in "PA and AQP modulation" under abiotic stress and identifies the lesser-explored landscapes, gaps in understanding, and the accompanying challenges. Finally, this review outlines the prospects of AMF in realizing sustainable agriculture and provides insights into potential thrust areas of research on AMF and abiotic stress.

Mycorrhizal fungi and Pseudomonas fluorescens application reduces root-knot nematode (Meloidogyne javanica) infestation in eggplant

Eggplant cultivation is subjected to attacks by numbers of pests and diseases from the nursery stage until harvest. Root-knot nematode (M. javanica) is one of the most significant restrictions in the successful cultivation of eggplant as it damages the crop year-round. One of the most essential classes of plant symbionts is arbuscular mycorrhizal fungi (AMF) and phosphate solubilizing bacteria (PSB), which significantly impact plant development, feeding, disease tolerance, and resistance to M. javanica. Eggplant seedlings were inoculated with two mycorrhizal fungi, Glomus mosseae (Gm) and Gigaspora gigantea (Gg), together with the phosphate-solubilizing bacteria (PSB) Pseudomonas fluorescens (Pf; ATCC-17400) under the presence of nematodes inoculation of Meloidogyne javanica as 1000 eggs of M. javanica in each pot. Observations were recorded for 9 morphological traits, 6 fruit morphometric traits using Tomato Analyzer (version 4) software program, and 4 fruit biochemical traits. Along with the data recorded for mycorrhization (%), number of galls and reaction to RKN. Plants inoculated with the consortium (Pf + Gm + Gg) performed substantially better for most traits. Furthermore, the eggplant plants treated with consortium developed the highest levels of fruit biochemical content along with the highest level of mycorrhization (68.20%). Except for certain fruit morphometric traits, the treatment containing Pf + Gg outperformed the treatment containing Pf + Gm. Overall, this research showed that AM fungi could be a sustainable solution to the eggplant RKN problem.

Ulva lactuca Extract and Fractions as Seed Priming Agents Mitigate Salinity Stress in Tomato Seedlings

The present study investigates the effect of Ulva lactuca extract as seed-priming agent for tomato plants under optimal and salinity stress conditions. The aims of this experiment were to assess the effect of seed priming using Ulva lactuca extract in alleviating the salinity stress tomato plants were subjected to, and to find out the possible mechanism of actions behind such a positive effect via means of fractionation of the crude extract and characterization. Salinity application decreased the plant biomass and altered different physiological traits of tomato. However, the application of Ulva lactuca methanol extract (ME) and its fractions (residual fraction (RF), chloroform fraction (CF), butanol fraction (BF), and hexane fraction (HF)) at 1 mg·mL^-1 as seed priming substances attenuated the negative effects of salinity on tomato seedlings. Under salinity stress conditions, RF application increased the tomato fresh weight; while ME, RF, and HF treatments significantly decreased the hydrogen peroxide (H₂O₂) concentration and antioxidant activity in tomato plants. The biochemical analyses of Ulva lactuca extract and fractions showed that the RF recorded the highest concentration of glycine betaine, while the ME was the part with the highest concentrations of total phenols and soluble sugars. This suggests that these compounds might play a key role in the mechanism by which seaweed extracts mitigate salinity stress on plants.

Mitigation of saline conditions in watermelon with mycorrhiza and silicon application

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Salt stress effects agronomic traits and uptake of minerals.

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Salt stress also enhanced the oxidative stress biomarkers like hydrogen peroxide (H₂O₂).

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Supplementation of Mycorrhiza enhances the agronomical traits and alleviates slat stress.

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Silicon application also mitigates the salt stress through modulating antioxidant enzymes.

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The combination of Mycorrhiza and Silicon were more effective than their individual effect.

Citrullus lanatus L. is critical vegetable for salinity stress. Arbuscular mycorrhizal fungi (AMF) and silicon treatments are known to help as bio-ameliorator of saline soils that can improve salinity tolerance in plants. But their combined effect has never been examined on watermelon therefore, present study investigated the effect of inoculation with the Arbuscular mycorrhizal fungi (AMF) along with silicon on the growth and yield parameters, antioxidant enzyme activities, pigment and mineral content of Citrullus lanatus L. plants grown during salt stress conditions. Outcomes from the study point out that salt stressed watermelon plants showed the best morphological and biochemical values when inoculated with Silicon (4 mM) + Glomus mosseae + Gigaspora gigantean. In addition, the plants inoculated by similar treatment demonstrated less osmotic activity, electrolyte leakage, as well as peroxide content. Treatments comprising Silicon (4 mM) with either Glomus mosseae and Gigaspora gigantean also performed significantly similar for most of the traits studied in the present investigation and better than the treatment only with either one of Glomus mosseae and Gigaspora gigantean. Antioxidant efficiency of melon was certainly appreciably enhanced after incubation with AMF and Si combination in salinity stress. Overall, the application of mycorrhiza and silicon can be considered to overcome the salinity stress in watermelon.

Assessing the Biostimulant Effects of a Novel Plant-Based Formulation on Tomato Crop

The aim of this research was to evaluate the biostimulant effects of an eco-product (EP) containing essential oils of rosemary and eucalyptus on tomato crop. Experiments were conducted to evaluate EP effects on plant growth and physiological parameters (e.g., chlorophyll content), total phenols and antioxidant activity, enzyme activities (e.g., catalase), plant macronutrient content and fresh tomato fruit quality. The application of an EP once (EP-1x) increased tomato plant height by 19%, stomatal conductance, and chlorophyll content compared to the control (sprayed with water). EP triplicate (EP-3x) application significantly increased yield (0.79 kg plant−1) compared to the control (0.58 kg plant−1). However, application of EP-3x was associated with a higher percentage of fruit cracking in comparison to the control. Total phenols and antioxidant activity were affected from both the use of EP and application frequency. EP application decreased by 27.3% the leaf damage index in comparison to the control. Nutrient content in leaves (N, Mg) was significantly decreased in the case of EP-3x treatment. Fruit firmness was decreased by 19.9% in the case of EP-1x application. Fruit marketability and tomato-like aroma, fresh weight and soluble solids did not differ among the treatments. Further research is required to examine the potential use of essential oils as biostimulants.